The disclosure relates generally to reliability of distributed antenna systems, and more particularly to techniques for enhancing spectral efficiency which may be used in a distributed antenna system.
Wireless communications services are expanding rapidly into an ever-wider array of communications media. Cellular communication and WiFi (or wireless fidelity systems), for example, are now commonplace and being used in a variety of commercial and public settings, such as homes, offices, shops, malls, libraries, airports, and the like. Distributed antenna systems (DAS) are commonly used to improve coverage and communication of cellular communication and WiFi communication systems. Distributed antenna systems (DAS) typically include a plurality of spatially separated antennas. The distributed antennas systems (DAS) communicate with a variety of such commercial communications systems to distribute their services to clients within range of the distributed antenna system.
Generally, distributed antenna systems (DASs) operate in a wide range of frequencies. For example, common designs for a single DAS require the system to provide services in a 700 MHz band, in a 2.7 GHz band and in bands between. In order to support future services, a DAS may even need to support services in frequency bands ranging from 100 Mhz to 3500 MHz and even above. Maintaining efficient operation over such a wide range of frequencies is not without challenges.
Consider that the frequency response of electronic components and circuits in such a wide range of frequencies is not constant. Therefore, system gain will vary over the frequency range and within each of the service bands for the DAS. Having a substantially constant gain over the operational frequency range of the DAS and within each of the service bands is desirable, otherwise, performance might differ (usually worsen) along the frequency range. For example, consider that in order to stay within the maximum transmission power level dictated by regulations, the maximum output power will have to be set at frequencies where the gain is maximal. For frequencies where the gain is lower, a lower power signal is transmitted and thus results in reduced Quality of Service (QoS) or Quality of Experience (QoE) performance to users.
Typically, the manufacturing process will attempt to account for some of these issues. For example, in order to avoid large variations in the frequency response, the DAS elements may be adjusted in the factory. Often, such adjustments call for setting a pre-determined average gain and as flat as possible frequency response within the service band. However, this may not be adequate for many installations.
For example, when installing a DAS that includes multiple cascading DAS elements, the overall errors in gain of each DAS element, combined with the variations in the frequency response due to imperfect matching issues, may accumulate and result in significant gain differences between different working points along the frequency range of the DAS and within each of the service bands. Particularly for complex DAS installations, it is required to manually adjust the power of most or all elements in a new installation of a DAS for compensating for the inadequate frequency response. Manual adjustment must be performed “in the field” and prior to system operation. Due to the large number of signal paths (from each base station to each remote unit), manual adjustment is a tedious, costly and inefficient process.
What is needed is a better way to improve gain over the operational frequency range of the DAS and within each of the service bands to better provide for optimizing DAS performances in terms of gain and power.
No admission is made that any reference cited herein constitutes prior art. Applicant expressly reserves the right to challenge the accuracy and pertinency of any cited documents.